


Expecto Patronum

by jazsy



Category: Harry Potter - J. K. Rowling, Sherlock (TV)
Genre: AU, Crossover, Dementors, Established Relationship, Fluff, John is basically Sherlock's real-life patronus, M/M, Potterlock, Teenlock
Language: English
Status: Completed
Published: 2012-12-27
Updated: 2012-12-27
Packaged: 2017-11-22 15:50:58
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,141
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/611527
Author URL: https://archiveofourown.org/users/jazsy/pseuds/jazsy
Summary: <blockquote class="userstuff">
              <p>John saves Sherlock from a soul-sucking monster. But it's fluff, really.</p>
            </blockquote>





	Expecto Patronum

A rough translation of _expecto patronum_ is, "I await a protector".

 

***

 

John's feet pound on the cobblestone streets of Hogsmeade as he tears through the small town, yelling Sherlock's name. It's just past midnight and he can see windows of houses around him lighting up, but he can't bring himself to be quieter, not when Sherlock's soul could be at stake (that idiot).

 

A door opens and a witch in curlers and a dressing gown steps out into the street in front of him, arms folded. John skids to a stop when he realizes it's Mrs. Hudson, who owns 221 Beetles, the potions shop and bakery. He and Sherlock go there on Hogsmeade weekends, Sherlock for things like salmon eyes and John for things like salmon cupcakes (surprisingly good).

 

"John Watson, is that you? Dear, what on earth are you doing down here at this hour? It isn't safe, you know, there's been talk of Dementors  flying about-"

 

"I know," John interrupts her, too desperate to be polite. "Sherlock had a theory about someone attracting them on purpose, said we would sneak down tomorrow after Herbology-"

 

Mrs. Hudson raises an eyebrow.

 

"-but then tonight we were supposed to meet up to, er, um-"

 

Mrs. Hudson is now smiling knowingly at him, and John knows he should be embarrassed but there isn't _time_.

 

"-anyway, he didn't show but he left a note saying he'd discovered something that couldn't wait, evidence might be gone by morning, and the _idiot_ went without me, that fucking-" 

 

John covers his face with his hands for a second before shaking himself and looking determinedly at Mrs. Hudson.

 

"I have to find him."

 

Mrs. Hudson nods worriedly and pats his shoulder, and John nods his thanks before taking off down the street again.

 

He reaches the edge of town and stands outside the Shrieking Shack, casting about for which way to go. He takes a few steps left and is suddenly hit with a feeling of dark, deep, clawing unhappiness. He stops, ponders, and backs up. He immediately feels better. He cautiously walks forward, to the right this time. Still fine.

 

John turns back to the left, takes a deep breath, and charges on.

 

***

 

There are many crevices and caves in the mountains surrounding Hogsmeade, and John has begun to despair of ever finding Sherlock when he comes upon a Ravenclaw scarf. Picking it up, he notes that it's still slightly warm and exhales in relief. He loops it around his neck and steps around a large piece of rock that juts out from the mountainside, only to come face to face with a nightmare.

 

Sherlock is lying on his back, and from his vantage point, John can't tell if he is awake or even breathing. The grotesque figure of a Dementor hovers above him, and John can see a thin line of silver light stretching from Sherlock's lips to the Dementor's gaping mouth. Every part of John feels cold and hopeless, and for a moment he cannot do more than stare blankly. His mind feels dark and empty.

 

 _Think_ , he tells himself. _Think, John_ , comes Sherlock's voice in his head, and he smiles-

-And then, like a match being struck, his mind is suddenly illuminated and he knows what he has to do.

 

John summons up the happy memory he'd used during his Advanced DADA class, Hufflepuff winning the Quidditch cup last year, and yells out, " _Expecto patronum!_ "

 

A large cloud of silvery vapor appears from John's wand, and it moves between Sherlock and the Dementor, and the Dementor does back away slightly. However, after a moment it begins to move forward again, slowly, as if it's moving through molasses.

 

 _Not strong enough_ , John realizes. _I'm not-_  

 _Wrong_ , comes Sherlock's voice again. _You simply need a happier memory. Quidditch, John? Dull. The happiest of your memories surely involve me._

 

And he's right. (Of course he's right.)

 

John closes his eyes and sees the memories in his mind, each as clear as he can make it.

 

_The two of them tumbling out of the Headmistress' office after the first mystery they'd solved together, grinning until they both broke and started giggling, shushing each other as they snuck down to the kitchens for a late-night snack; their first kiss, shy and sweet, in the empty classroom Sherlock had appropriated as a potions lab; Sherlock waiting for him after a Quidditch match, John's Hufflepuff scarf tied around his neck instead of his own; Sherlock's smile, tinged with awe, on his last birthday when John had handed him the treasure map that led to his gift; the way John feels whenever Sherlock is touching him, like magic is going to start sparking off his skin itself._

 

Opening his eyes, John raises his wand, sure and steady, and once again utters the spell.

 

His first thought is that he's failed again, since the silver mist that appears from his wand is smaller than before. However, it quickly takes on a life of its own, forming the shape of a hedgehog that runs at the Dementor, growing as it does so. It seems to push at the Dementor until it moves away, and then chases it off into the night.

 

John runs to Sherlock, who is coughing and trying to sit up. "Well done, John," he croaks. "A corporeal patronus. You have to teach me how to do that."

 

John can only grin shakily and nod, wrapping his arms around Sherlock's shoulders and resting his forehead against Sherlock's temple. One of Sherlock's hands brushes up to rest on the back of John's neck.

 

There's a popping noise, followed by several more and then voices and lights in the dark. The familiar voice of Auror Lestrade calls out, "Holmes? Watson? That you?"

 

"Yeah," John answers, getting to his feet and pulling Sherlock with him as Lestrade walks up to them, shaking his head already in exasperation. "How did you-"

 

"Martha Hudson called me. Your turn. Start explaining."

 

***

 

John and Sherlock get banned from Hogsmeade weekends for three months, which actually doesn't feel that bad on days like this one when they find themselves completely alone, lying in the grass on the edge of the lake. They'd both been reading, but Sherlock has thrown his book aside in favor of practicing the patronus he mastered last week. His silver otter swims lazily over their heads, and for awhile John has been looking at it instead of his book, so he gives up and puts the book away. With a flick of his wand and a quiet murmur, his own silver hedgehog appears.

 

 The otter swims around the hedgehog, coming to rest right in front of it. The hedgehog leans forward to nudge the otter's ear playfully with its nose, and John smiles as he feels Sherlock's fingers interlace with his own.

 

Not bad at all.

**Author's Note:**

> Inspired by [this picture](http://devinleighbee.tumblr.com/image/38918699293) by [devinleighbee](http://devinleighbee.tumblr.com/) on tumblr.


End file.
